What is the Difference Between Mosaic Down Syndrome and Down Syndrome?
🆚 Go to Comparative Table 🆚Mosaic Down syndrome and Down syndrome are both genetic disorders involving an extra copy of chromosome 21. However, there are some differences between the two:
- Chromosome Distribution: In Mosaic Down syndrome, not all cells have an extra copy of chromosome 21. Some cells have the typical two copies, while others have three copies. This results in a mixture of cells, which is why it is referred to as "mosaicism". In contrast, all cells in individuals with Down syndrome have an extra copy of chromosome 21.
- Symptoms and Characteristics: People with Mosaic Down syndrome may have fewer or less evident characteristics of Down syndrome due to the presence of some cells with a typical number of chromosomes. The exact features can vary widely from person to person, with some having few or no characteristics of the condition and others having more.
- Prevalence: Mosaic Down syndrome is a rare form of Down syndrome, affecting about 1 to 2% of people with Down syndrome.
Diagnosis of Mosaic Down syndrome is typically done through a chromosome study, where doctors analyze 20 different cells. The percentage of cells with an extra chromosome 21 determines the level of mosaicism. For example, if 5 cells have 46 chromosomes and 15 have 47 chromosomes, the person has a 75% level of mosaicism. Ongoing research is attempting to determine if there are any differences in the health of people with Mosaic Down syndrome depending on how the mosaicism occurred or if the percentage of mosaicism can predict the person's health outcomes.
Comparative Table: Mosaic Down Syndrome vs Down Syndrome
Mosaic Down syndrome and Down syndrome are both genetic conditions related to an extra copy of chromosome 21. However, there are some differences between the two. Here is a comparison table highlighting the key differences:
| Feature | Mosaic Down Syndrome | Down Syndrome |
|---|---|---|
| Chromosome Composition | A mix of cells with a normal pair of chromosome 21 and cells with three copies of chromosome 21 | All cells have three copies of chromosome 21 |
| Occurrence | Identified in about 2% of people with Down syndrome | More common, occurring in about 90-95% of individuals with Down syndrome |
| Symptoms | Children may have fewer symptoms due to the presence of cells with a typical number of chromosomes | Symptoms are more consistent across individuals |
Both Mosaic Down syndrome and Down syndrome are genetic conditions related to an extra copy of chromosome 21, but Mosaic Down syndrome is a rarer form and involves a mix of cells with different chromosome compositions.
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